1. Field of the Invention
The invention relates to an apparatus and method for die cutting in a press and in particular to die cutting cardboard in a clam shell press.
2. Description of the Prior Art
Containers and cartons are manufactured by die cutting, sometimes with intricate shapes. In the basic die-cutting process sharp metal edges in the form of a die are brought with pressure against a cardboard surface to cut through the cardboard and are then retracted. When cutting complex shapes in corrugated cardboard, a substantial amount of pressure must be brought on the die to cut through the cardboard and the knife edge of the die must be forced into the cardboard, which in turn is forced with extreme accuracy through the cardboard against a solid backing plate, typically within a few thousandths of an inch.
As the knives of the die wear or when the die is originally made ready, a displacement of the knife edges even by a few thousandths of an inch causes the cut through the cardboard to be unclean and the product becomes unusable. A "make ready" process must be performed wherein portions of the die knife edges are shimmed by layers of adhesive tape. Cardboard tape of a few thousandths of an inch or metal shims ranging from one to ten thousandths of an inch are placed between selected portions of the die's rear edge and the surface of the press and are used to cleanly force the die into the cardboard. The make-ready process must be practiced to both to set up the die when first cutting and to adjust the die as it wears during a cutting project. If the make ready process is not at first successful, the die must be removed from the press readjusted and again tested until satisfactorily adjusted. This is a process which can be time consuming even for a skilled press operator.
A method and apparatus are needed whereby this make-ready process can be simplified.